> But if there are only a few of them, and a large fleet is being renewed, I suppose it can make sense from a fleet management point of view to renew the few perfectly current ones as well.

I suspect that had something to do with it. The Core Ultras came out of Dells, and as mentioned, the industry around here uses HP almost exclusively. (The rest of that load was HP, only about 1% were those Dells.) Some dogmatic system administrator probably said "We we are only supposed to use HP, get those Dells out of here!"